Production of hydroxylammonium sulphate



June 29,1943. f "P. F. TRYON T 2,322,958

PRODUCTION OF HYDROXYLAMMONIUM SULPHATE Filed June 6, 1941 1'. 90 l 3 "2 v so e 5 v (A) VOLUMES OF SOLVENTS 3g (0) H VOLUMES OF SOLVENTS 53 1 VOLUME or SOLVENT EI 1o so as 90 9s METHANOL CONCENTRATION OF AQUEOUS METHANOL (PERCENT BY VOLUME) FIGURE 1 PERCENT YIELD OF HYDROXYLAMMONIUM SULFATE TEMPERATURE or FILTRATION or REACTION MIXTURE FIGURE 11 ll-l r- I 6 2 z 0 o fig I 75 J 'z' i u 0 E E a E a0 a5 9o PERCENT PURITY OF HYDROXYLAMMONIUM ACID SULFATE USED FIG U R E III INVENTORW ATTORNEYM Patented 29, 1943 z'szzsss 'raoouc'rrou or HIDIOXYLAMMONIUH surrnsrn rm, 1-; Tryon, 'l'erre mm, ms,

Commercial Solvents Corporation, 'lerre Iaryland nun-- corporation oi Application 1.... s, 1941, Serial No. seem 3 Claims. (cuss-m)- acid sulphate or a crude solution memos, with The presentinvenflon relates to a novel process for the production oi hydroxylammonium sulphate. More particularly, it concerns. aprocess i'or obtaining substantially pure hydrosylammonium sulphate by treating hydroxylammonium acid sulphate, or crude solutions thereof, with an aqueous solution oi methyl alcohol.

Hydroxylammonium acid sulphate is generally regarded as an equilibrium mixture consisting of hydronlammonium sulphate, sulphuric acid. and

hydroxylsmmonium acid sulphate, as may he illustrated by the following equation:

2 un=omnsoq==mmom sm+msm Ifitis desired to obtain hydroxylammonium sulphate therefrom, it will obviously be necessary totreatthemixtureinsuchamannerthatthe equilibriumisdisplacedtowardtheright. Itwlll alsoheapparent thatinoidertoattainthisob-' iect, a reagent should be employed. which forms an insoluble substance with sulphuric acid, or whichisapoorsolvent iorhydroxylammcnium sulphate, andis either a good solvent for sulphuric acid,oriscapableoiiormingasolution containing. no compound with acid which is a poor solvent fonsaid hydmxylammoniumsulphate a Inattemptingtosolvethlsprohlmtherelnve beennmnereusmethodsproposedsomeolwhich ing outthisprocess,.the precipitate oicalfcium sulphate, thus iormed. is separated from the aqueoussolutionothydroxylammonimnsulphate hymeansoiflltratimandthcnltratelstben evaporated in order to obtain hydroxylammoniumsulphate. 'lhehydroxylaminoniumsulphate,thus,secured,isgenerallyonlyahout00 percentpm'e,andmustbediasolvedandrecrystallisedi'romasuitablesolventinosdertoobtahi to Hate,

aqueous methanol toobtain crystalline hydroxylammonium sulphate in yields that are appreciably in excess oi those obtainable by employing pure methanol. To secure hydronlammonium sulphateinincreasedylelds,inthei'ormoia crystalline precipitate, by the addition oi water tothe'methanol is entirelycontrary to the results whichwouldnormallyheexpectedinviewoi the fact that wateritseli is a goodsolvent ior hy-- dronlammonium sulphate. Ordinarily it would be anticipated, under such circumstances, that the solvent power of such methanol solutions for hydroxylammonium sulphate would be substantially increased, rather than decreased. Based upon-the discovery oithe above phenomenon, a

commercially practical method for converting hydroxylammonium acid sulphate into hydroxylammonium sulphate, has now been provided.

In accordance with my invention, hydroxyiammonium acid sulphate, or a crude solution thereof, is slowly introduced into an aqueous methanol solution, and the mixture thoroughly agitated during the addition of said hydroxylammonium acid mlphate. As previously stated, the. h!- droxylammonium acid sulphate is thought to be composed oi an'equilihrium mixture consisting of hydroxylammonium sulphate, sulphuric acid,

and hydroxylammonimn acid sulphate. Upon contaet'with aqueous methanol, the sulphuric acidis dissolved therein to give a solution in which hydroxylammcnium sulphate is substantiallyinscluble.thusdisplacingtheequilibrium' to the right viililtll substantially all 01' the hy- 0d drox'ylammoniumacid sulphate has-been converted intofhydrmlammonlum sulphate. The hydroxylammonium sulphate, thus formed, being insoluble in the resulting medium, precipitates the product in asubstantiallypure state. Itls, evident that the industrial application oi such a process would entail the handling oiexcasive quantiticsoisolutions. as wellasthe tedious and expensive operation or evaporating said solutions.

Ihavenovvdiscoveredamethodioi'securing I hydroxylammonium sulphate i'rom' hydroxylammonium acid sulphate in a-suhstantially pure state, andinconslstentlyhlghylelds, which comprises essentially treating hydroxylammonium thereiro'm asawhite, crystalline solid. Itis then separatediromsaidmedium byflrstcoolingthe latter to approximately 25' 0., and filtering under vacuum, after which the crystalline hydroxylammonium sulphate is washed with methanol. preierablyin'theiorm of an 85 per centsolution,

andthendriedioraperiodoti'romthreetonve' hours -at'a temperature oi. from 50-00 C. The

IIICMOIQDPIOMIDWWMMMP ilyand substantiaiiycompletelyrecovered trom the nitrate by Thus. by distilling this mixture andrecovering the methanol, the total volume thereof employed in carrying out .my invention, remains relatively small, since the saidmethanolthusobtainedmayhereusedior an indefinite period inthe iirst step 01' my procetc, Also, the sulphm'icacid remaining in the still residue may be recovered, and used as a reagent in the preparation of additional hydroxylammonium acid sulphate.

The process of the present invention is readily adapted to commercial application because of the relatively small operation costs. The present invention constitutes a further advantage over prior art methods in that it is capable of being eiiiectively operated on a commercial scale without requiring the handling of undesirably lai'ge volumes of reagents.

In following the process of the present tion, particular attention should be given to the concentrations of the aqueous methanol solutions, as well as the relative volumes thereof employed. Likewise, the temperature at which the process is carried out. and the purity of hy-' droxylammonium acid sulphate employed, are

latter being of 90 per cent purity, was employed.

The results show that the yield of hydroxylammonium sulphate, obtained by the treatment of hydroxylammonium acid sulphate with aqueous methanol, increases as the filtration temperature is decreased from 25 C. to C. In all cases the purity of the hydroxylammonium sulphate obtained at the various temperatures listed in Fig-.1

ure 2, did not fall below 96 per cent, and in most instances was found to be of 98 per cent purity.

invenadditional factorswhich require careful attention inorder that optimum results may be obtained.

The accompanying drawing is a detailed graphical representation illustrating the dependency of the successful operation of the present invention upon the factors referred to above.

The curves of Figure 1 represent the yields obtained by treating hydroiwlammoniumacid sulphate of 92 per cent purity with aqueous methanol solutions of varying concentrations and volumes. The concentrations and volume of the methanol solutions, employed in carrying out my increases, the yield of hydroxylammonium suiphate also increases. Obviously, therefore, for optimum results, it will be desirable to use hydroxylammonium acid sulphate of the highest process, will be found to vary within certain limits, and ingeneral it may be said that aqueous solutions consisting of from 7H0 per cent methanol, may be utilized. Otherwise stated, the water content of the reaction mixture should not appreciably exceed 15.5 per cent by weight, based upon the total weight of said mixture, and should constitute at least 4.3 per cent by weight of said mixture. Thus it will be apparent that although the hydroxylammonium acid sulphate employed in my process generally contains no water as an impurity, aqueous solutions of said hydroxylammonium acid sulphate may be utilized provided the water content thereof is such that th per cent by weight. of water in the reaction mixture lies within the range specified above.

The desired volume to be employed for methanol solutions of given concentrations, may be readily ascertained by reference to Figure 1. As may be seen from a brief inspection of Figur 1, for a solution of given methanol concentration, the highest yields of hydroxylammonium sulphate are generally secured by the use of one and one-fourth volumes of aqueous methanol per volume of hydroxylammonium acid sulphate, al.-

though the yields secured when using from one and one-half to two volumes of solvent, are comparable to those obtained in the former case. It will also be evident, from Figure 1, that fora given relative volume of aqueous methanol, the highest yield of hydroxylammonium sulphate are secured with 85 per cent methanol. In terms of per cent by weight of water contained in the reaction mixture, this figure may vary from 6.4 to 9.45 per cent, depending of course upon whether one or two volumes of 85 per cent methanol per volume of hydroxylammonium acid sulphate have been employed.

Figure 2 illustrates the extent to which the illtration temperature affects the yield of hydroxylammonium sulphate. In obtaining the data used inconstructing the curve of Figure 2, one and one-fourth volumes of 80 per cent methanol per volume of hydroxylammonium acid s p te, the

purity that is practically possible.

In this connection, I have found that hydroxylammonium acid sulphate is readily'obtainable in large quantities, and in a substantially anhydrous and relatively pure state, as one of the principal products of the process described in U. S. Pat. No. 2,113,812 to S. B. Lippincott. According to this reference, aliphatic monocarboxylic acids, together with a substantial quantity of hydroxylammonium acid sulphate, are readily obtained by reacting a primary nitroparaflin with approximately an equimolecular quantity of sulphuric acid in the presence of at least one mole of water per mole of nitroparafiln. At the conclusion of the reaction period, two distinct layers are observed,

.the upper layer consisting of aliphatic monocarboxylic acid, unreacted nitroparaflin, and a small quantity of sulphuric acid, while the lower layer is found to be composed principally of hydroxylammonium acid sulphate, together with relatively small amounts of'a-mmom'um hydrogen sulphate, sulphuric acid, and aliphatic monocarboxylic acid. The lower layer may be drawn off by any convenient means, and immediately used in the process of the present invention, without further purification. The hydroxylammonium acid sulphate, obtained in the lower layer, is present therein in the form of a substantially anhydrous super-cooled liquid, and is obtainable in a state of purity as high as per cent, provided the starting materials employed in the abovementioned reaction are sufiiciently pure.

- It will be evident, from the foregoing disclosure, that the present invention is subject to numerous modifications. .For example, although it might be assumed from the above description that the present invention is applicable only to batch processes, it may be employed in continuous methods with equal success, by the use of obvious modifications. In general, it may be said that the present invention is intended to cover, by the terminology employed in the appended claims, all features of patentable novelty inherent therein.

.The compound hydroxyl-ammonium-sulphatewhich I form is more commonly known as hydroxylamine sulphate.

Having now described my invention, what I claim is:

1. In a process for the production of hydroxylammonium sulphate, the step which comprises introducing hydroxylammonium acid sulphate into an aqueous methanol solution, wherein the water content oi the resulting mixture represents from about 4.3 to 15.5 per cent by weight of said mixture, and separating the resulting crystalline hydroxyiammonium sulphate. g

. 2. In a process (or the production of hydroxylammonium sulphate, the step which comprises introducing hydroxylammonium acid sulphate into an aqueous methanol solution in a ratio or from about 1.25 to 1.50 volumes 0! said aqueous methanol solution per volume or hydroxylam monium acid sulphate, wherein the water content of the resulting mixture represents from about 4.55 to 13.0 per cent by weight of ma mixture,

and separating the resulting crystalline hydroxylmately 1.6 to as per cent by weight of ma mixture, and separating the resulting crystalline hydroxylammonium sulphate.

Plum 1-. TRYON. 

